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PubMed1990

Topologically restricted appearance in the developing chick retinotectal system of Bravo, a neural surface protein: experimental modulation by environmental cues.

A novel neural surface protein, Bravo, shows a pattern of topological restriction in the embryonic chick retinotectal system. Bravo is present on the developing optic fibers in the retina; however, retinal axons in the tectum do not display Bravo. The appearance of Bravo in vitro is modulated by environmental cues. Axons growing out from retinal explants on retinal basal lamina, their natural substrate, express Bravo, whereas such axons growing on collagen do not. Retinal explants provide a valuable system to characterize the mechanism of Bravo restriction, as well as the cellular signals controlling it. Bravo was identified with monoclonal antibodies from a collection generated against exposed molecules isolated by using a selective cell surface biotinylation procedure. The NH2-terminal sequence of Bravo shows similarity with L1, a neural surface molecule which is a member of the immunoglobulin superfamily. This possible relationship to L1, together with its restricted appearance, suggests an involvement of Bravo in axonal growth and guidance.

Amino Acid Sequence↗

PubMed1991

The axonally secreted protein axonin-1 is a potent substratum for neurite growth.

Axonin-1 is a neuronal glycoprotein occurring both as a membrane-bound and a secreted form. Membrane-bound axonin-1 is predominantly located in membranes of developing nerve fiber tracts and has recently been characterized as a cell adhesion molecule; the soluble form is secreted from axons and accumulates in the cerebrospinal fluid and the vitreous fluid of the eye. In the present study, we addressed the question as to whether secreted axonin-1 was released in a functionally competent form and we found that it strongly promotes neurite outgrowth when presented to neurons as an immobilized substratum. Neurite lengths elaborated by embryonic dorsal root ganglia neurons on axonin-1 were similar to those on the established neurite-promoting substrata L1 and laminin. Fab fragments of axonin-1 antibodies completely inhibited neurite growth on axonin-1, but not on other substrata. In soluble form, axonin-1 had an anti-adhesive effect, as revealed by perturbation of neurite fasciculation. In view of their structural similarity, we conclude that secreted and membrane-bound axonin-1 interact with the same growth-promoting neuritic receptor. The fact that secreted axonin-1 is functionally active, together with our previous findings that it is secreted from an internal cellular pool, suggests a functional dualism between membrane-bound and secreted axonin-1 at the site of secretion, which is most likely the growth cone. The secretion of adhesion molecules could represent a powerful and rapidly acting regulatory element of growth cone-neurite interactions in the control of neurite elongation, pathway selection, and possibly target recognition.

Animals↗

PubMed1991

Structure of a new nervous system glycoprotein, Nr-CAM, and its relationship to subgroups of neural cell adhesion molecules.

We have identified and characterized a new glycoprotein in the chicken nervous system using immunological and molecular biological methods and we have examined its tissue distribution. Analysis revealed that this protein is very similar in structure to the chicken neuron-glia cell adhesion molecule, Ng-CAM, and to mouse L1. cDNA clones encompassing the entire coding sequence of this Ng-CAM related molecule, called Nr-CAM, have been isolated and sequenced. A glycoprotein containing one major component of Mr 145,000 on SDS-PAGE was purified from brain by lentil lectin affinity chromatography and FPLC, and its amino-terminal sequence was identical to that predicted from the Nr-CAM cDNA. The complete cDNA sequence encodes six Ig-like domains, five fibronectin type III repeats, a predicted transmembrane domain, and a short cytoplasmic domain. On Northern blots, nucleic acid probes for Nr-CAM recognized one major RNA species of approximately 7 kb and much lesser amounts of larger RNAs. Most of the same probes hybridized to single bands on genomic Southern blots, suggesting that Nr-CAM is encoded by a single gene that may be alternatively processed to yield several mRNAs. In support of this notion, two Nr-CAM cDNA clones had a 57-bp sequence located between the second and third Ig-like domains that was not found in two other Nr-CAM cDNA clones, and two other clones were isolated that lacked the 279-bp segment encoding the fifth fibronectin-like type III repeat. Antibodies against the purified protein and synthetic peptides in Nr-CAM both recognized a predominant Mr 145,000 species and a much less prevalent species of Mr 170,000 in neural tissues. Levels of Nr-CAM expression increased in the brain until approximately embryonic day (E) 12, followed by slightly lower levels of expression at E18 and after hatching. Immunofluorescent staining with anti-Nr-CAM antibodies showed that most neurons in the retina were positive at E7 and the pattern of expression became restricted to several layers on neuronal cell bodies and fibers during development. Anti-Nr-CAM antibodies labeled specifically cell surfaces on neurons in culture. Although the structure of Nr-CAM resembles that of chicken Ng-CAM and mouse L1, the identity with each of these neural CAMs does not exceed 40%. The differences indicate that Nr-CAM is distinct from Ng-CAM and L1, but there are sufficient similarities to suggest that all of these molecules are members of a subgroup of neural CAMs in the N-CAM superfamily.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1981

Cytoplasmic actin in postsynaptic structures at the neuromuscular junction.

We used an antibody prepared against Aplysia (mollusc) body-wall actin that specifically reacts with certain forms of cytoplasmic actin in mammalian cells to probe for the presence of actin at the neuromuscular junction. Immunocytochemical studies showed that actin or an actinlike molecule is concentrated at neuromuscular junctions of normal and denervated adult rat muscle fibers. Actin is present at the neuromuscular junctions of fibers of developing diaphragm muscles as early as embryonic day 18, well before postsynaptic folds are formed. These results suggest that cytoplasmic actin may play a role in the clustering or stabilization of acetylcholine receptors at the neuromuscular junction.

Actins↗

PubMed1984

Chick myotendinous antigen. II. A novel extracellular glycoprotein complex consisting of large disulfide-linked subunits.

This report describes the biochemical characterization of a novel extracellular matrix component, " myotendinous antigen," which appears early in chick limb morphogenesis at sites connecting developing muscle fibers, tendons, and bone ( Chiquet , M., and D. Fambrough , 1984; J. Cell Biol., 98:1926-1936). This extracellular matrix antigen is a major component of the secretory proteins released into the medium by fibroblast and muscle cultures; the soluble form is characterized here. This form of myotendinous antigen is a large glycoprotein complex consisting of several disulfide linked subunits (Mr approximately 150,000-240,000). The differently sized antigen subunits are related, since they yielded very similar proteolytic cleavage patterns. M1 antibody can bind to the denatured subunits. The antigen subunits, as well as a Mr approximately 80,000 pepsin-resistant antigenic domain derived from them, are resistant to bacterial collagenase. Despite possessing subunits similar in size to fibronectin, myotendinous antigen appears to be both structurally and antigenically unrelated to fibronectin or to other known extracellular matrix components. About seven times more M1 antigen per cell nucleus was released into the medium in fibroblast as compared to muscle cultures. In muscle conditioned medium, myotendinous antigen is noncovalently complexed to very high molecular weight material that could be heavily labeled by [3H]glucosamine and [35S]sulfate. This material is sensitive to chondroitinase ABC and hence appears to contain sulfated glycosaminoglycans. We speculate that myotendinous antigen might interact with proteoglycans on the surface of muscle fibers, thereby acting as a link to tendons.

Animals↗

PubMed1967

Acetylcholine and calcium on membrane permeability and contraction of intestinal smooth muscle.

Acetylcholine elicited a sustained contraction and an increase in potassium efflux in longitudinal muscle isolated from the guinea pig ileum. Stepwise increases in the calcium concentration of the bathing medium, from 0.06 to 36 mM generally reduced the increase in potassium efflux, but had a complex effect on the mechanical response. Contractions produced by high levels of acetylcholine became progressively larger or remained at a high magnitude as the calcium concentration was increased. Contractions produced by low levels of acetylcholine also improved initially, but were depressed again by the highest concentration of calcium introduced. Ethanol, in the appropriate concentration, inhibited completely the acetylcholine-induced contraction without reducing the increase in potassium efflux. Calcium reversed this effect. Both extracellular calcium and ethanol depressed the large, transient increase in muscle tone developed by fibers that were preincubated in a high calcium medium and then exposed to a calcium-free medium. These findings suggested that extracellular calcium ions react with two different sites in the membrane, a stabilizing site and a storage site. A muscle contraction is activated by calcium ions which diffuse from the storage site to the myoplasm. Calcium ions reacting with the stabilizing site impede this diffusion process. Part of the stimulatory effect of acetylcholine is derived from its capacity to counteract the action of calcium at the stabilizing site.

Acetylcholine↗

PubMedDate not supplied

Subculture of chondrocytes on a collagen type I-coated substrate with suppressed cellular dedifferentiation.

To evaluate the degree of cellular dedifferentiation, subculture of chondrocytes was conducted on a surface coated with collagen type I at a density of 1.05 mg/cm(2). In the primary culture, most of the cells were round in shape on the collagen (CL) substrate, whereas fibroblastic and partially extended cells were dominant on the polystyrene plastic (PS) substrate. Stereoscopic observation revealed that the round-shaped cells on the CL substrate were hemispherical with nebulous and punctuated F-actin filaments, whereas the fibroblastic cells on the PS substrate were flattened with fully developed stress fibers. This suggested that cell polarization was suppressed during culture on the former substrate. Although serial passages of chondrocytes through subcultures on the CL and PS substrates caused a decrease in the number of round-shaped cells, the morphological change was appreciably suppressed on the CL substrate, as compared with that on the PS substrate. It was found that only round-shaped cells formed collagen type II, which supports the view that cellular dedifferentiation can be suppressed to some extent on the CL substrate. Three-dimensional cultures in collagen gel were performed with cells isolated freshly and passaged on the CL or PS substrate. Cell density at 21 days in the culture of cells passaged on the CL substrate was comparable to that in the culture of freshly isolated cells, in spite of a significant reduction in cell density observed in the culture of cells passaged on the PS substrate. In addition, histological analysis revealed that the expression of glycosaminoglycans and collagen type II was of significance in the collagen gel with cells passaged on the CL substrate, and likewise in the gel with freshly isolated cells. This indicated that the CL substrate could offer a monolayer culture system for expanding chondrocyte cells.

Adsorption↗

PubMed2002

Mixed-methods resistance training increases power and strength of young and older men.

PURPOSE: This study examined the effects of mixed-methods resistance training on young and older men to determine whether similar increases in muscle power were elicited. METHODS: Effects of 10 wk of a periodized resistance-training program designed to increase muscle size, strength, and maximal power on isometric squat strength, time course of force development, muscle fiber characteristics, and muscle activation (iEMG), as well as force and power output during squat jumps, were compared in young (YM, 30 +/- 5 yr, N = 8) and older men (OM, 61 +/- 4 yr, N = 10). RESULTS: Isometric squat strength was higher in the YM compared with OM at all testing occasions and increased over the training period by 23 +/- 15% and 40 +/- 42% for the YM and OM, respectively. The early phase of the force-time curve was shifted upward in both groups over the course of the training. During the squat jumps, the YM produced higher force and power at all test occasions and at all loads tested compared with the OM. The YM increased power output by 15 +/- 14%, 33 +/- 16%, and 26 +/- 12%, and the OM by 7 +/- 5%, 36 +/- 23%, and 25 +/- 16% for the 17 kg, and 30% and 60% 1RM loads, respectively. CONCLUSION: Although the results of this study confirm age-related reductions in muscle strength and power, the older men did demonstrate similar capacity to young men for increases in these variables via an appropriate periodized resistance-training program that includes rapid, high-power exercises.

Adult↗

PubMed2001

Augustus V. Waller and plastic surgery.

Augustus V. Waller's name is associated eponymously with the regressive changes in transected nerves. This article intends to present the many other aspects of Waller's scientific ventures. Apart from pioneering intravital microscopy, Waller made significant contributions to the understanding of the process of tissue inflammation. In addition to his observations of the degenerative changes in severed nerve fibers, he developed a concept of trophic dependence that is relevant for the management of the regeneration of peripheral nerves in plastic surgery.

England↗

PubMed2002

Mixed nerve suture facilitated by enzyme-staining techniques.

Identification of motor and sensory fascicles to correctly match the motor and sensory fascicles helps surgeons to correctly align nerve stumps. Motor fibers, with their high cholinesterase activity, can be differentiated from sensory fibers. I developed a new modification that requires less than 1 hour and shows clearer differentiation compared with other histochemical techniques. In my clinical research, proximal stumps can be stained as long as 16 months after injury, however, distal stumps cannot be stained after 5 days. After 5 days, this staining could provide useful proximal information and distal fascicles may be identified by anatomic or topographical knowledge. I think this staining is especially useful in proximal nerve lesions and nerve injuries that require nerve graft within 4 days after injury. Also, this technique is useful in functioning muscle transfer to find motor fascicles and, in a sensate flap, to identify the sensory fascicle.

Journal Article↗

PubMed1983

Ultrastructural cytochemical demonstration of elastin in the matrix of salivary gland tumors.

Following light microscopic survey of the incidence of elastic tissue in 80 salivary gland tumors, tissue samples from 14 pleomorphic adenomas, three myoepitheliomas, and eight adenoid cystic carcinomas were processed for cytochemical demonstration of elastin with the tannic acid stain for ultra-thin sections. For comparative study, some other tumor types devoid of elastic tissue at the light microscopic level and non-neoplastic submandibular glands were also investigated. Elastic deposits of varying amounts were clearly revealed on the basal-lamina-like material and/or masses of microfibrils in the matrix close to the neoplastic myoepithelium and, to a lesser degree, immediately beneath the non-neoplastic myoepithelium. None of the other tumor types without myoepithelial differentiation contained elastic deposits closely associated with the neoplastic cells. Intimate topographical relationship of such as immature elastic fiber or developing elastic tissue to the neoplastic myoepithelial cells strongly indicated the primary origin of elastic components from these cells. It is postulated that the potential of salivary tumor cells to produce elastin is regarded as an indicator of their myoepithelial nature or differentiation.

Adenoma↗

PubMed1978

The existence of smooth muscle adjacent to the Schlemm's canal of the normal albino rat eye.

The existence of smooth muscle adjacent to the rat aqueous outflow pathway was confirmed in this study. The smooth muscles ran parallel to the Schlemm's canal and reached the level of the posterior end of Schlemm's canal. The characteristics of these muscles were similar to smooth muscles in other organs. The existence of smooth muscle in this region depends on the fact that the rat eye lacks the scleral spur and the poorly developed meridional fibers of ciliary muscles come to lie close to the endothelial cells of Schlemm's canal. The innervation and function of these smooth muscles are unknown.

Animals↗

PubMed2003

Initial burst measures of release kinetics from fiber matrices.

A comprehensive axisymmetric diffusion model of drug release from a fiber is developed to account for both the initial burst (IB) phenomenon as well as the later diffusion-dominated release. This model is an enhancement over previous models in that a set of four IB parameters are calculated, which both describe the initial burst phenomenon as well as improve the fit for the diffusion-dominated release phase. This model is also an enhancement over previous models in allowing: finite dissolution volumes, finite stirring levels of the medium, and user-specified initial drug dispersion within the device. Five different drug release data sets are used to verify the model and to derive values for the IB parameters. Two of the data sets are from experiments conducted in this study, and the other three sets are from previously published data. These data sets were selected to cover a wide range of possibilities, i.e., from nearly 0% to nearly 100% of the total drug release during IB, yet the model handles all cases equally well.

Algorithms↗

PubMed1985

Evaluation of local blood flow velocity in proximal and distal coronary arteries by laser Doppler method.

A high resolution laser Doppler velocimeter using an optical fiber was developed to evaluate detailed characteristics of phasic blood flow in the coronary artery. Local blood flow velocities were measured in the proximal (0.27 +/- 0.05 cm i.d.) and the distal portion (0.09 +/- 0.02 cm i.d.) of the left circumflex coronary artery of anesthetized, open-chest dogs. The velocity waveform in the central axial region of the vessel and the velocity profile across the vascular lumen were compared in the proximal and the distal portions.

Animals↗

PubMed2002

Brevican-deficient mice display impaired hippocampal CA1 long-term potentiation but show no obvious deficits in learning and memory.

Brevican is a brain-specific proteoglycan which is found in specialized extracellular matrix structures called perineuronal nets. Brevican increases the invasiveness of glioma cells in vivo and has been suggested to play a role in central nervous system fiber tract development. To study the role of brevican in the development and function of the brain, we generated mice lacking a functional brevican gene. These mice are viable and fertile and have a normal life span. Brain anatomy was normal, although alterations in the expression of neurocan were detected. Perineuronal nets formed but appeared to be less prominent in mutant than in wild-type mice. Brevican-deficient mice showed significant deficits in the maintenance of hippocampal long-term potentiation (LTP). However, no obvious impairment of excitatory and inhibitory synaptic transmission was found, suggesting a complex cause for the LTP defect. Detailed behavioral analysis revealed no statistically significant deficits in learning and memory. These data indicate that brevican is not crucial for brain development but has restricted structural and functional roles.

Animals↗

PubMed2002

Deletion of the laminin alpha4 chain leads to impaired microvessel maturation.

The laminin alpha4 chain, a component of laminin-8 and -9, is expressed in basement membranes, such as those beneath endothelia, the perineurium of peripheral nerves, and around developing muscle fibers. Laminin alpha4-null mice presented with hemorrhages during the embryonic and neonatal period and had extensive bleeding and deterioration of microvessel growth in experimental angiogenesis, as well as mild locomotion defects. Histological examination of newborn mice revealed delayed deposition of type IV collagen and nidogen into capillary basement membranes, and electron microscopy showed discontinuities in the lamina densa. The results demonstrate a central role for the laminin alpha4 chain in microvessel growth and, in the absence of other laminin alpha chains, in the composition of endothelial basement membranes.

Anemia↗

PubMed1976

Eelctrophysiologic and ultrastructural characteristics of the canine tricuspid valve.

Collagen extending from chordae tendineae sweeps into each tricuspid leaflet in a loose fanlike arrangement merging with the annulus. Each leaflet contains variable amounts of cardiac muscle in continuity with right atrial muscle; valve fibers are sparse, and scattered myofibers and/or bundles of myofibers usually extend only 2-3 mm into the leaflet body. Valve myofibers are structurally identical to working right atrial muscle but are 2-3 mum in diameter compared to 5-7 mum in working muscle. Electrical stimulation of the low right atrial wall often induces propagated activity in the leaflet. Transmembrane recordings obtained from isolated Tyrode superfused leaflets showed low maximum diastolic potential, action potential amplitude, and rate of depolarization; action potentials usually had prominent plateaus. Excitation of discrete regions in tricuspid leaflets did not excite atrial wall, but valve muscle fibers often developed spontaneous diastolic depolarization and automaticity after stretch or exposure to catecholamines Automaticity was suppressed by acetylcholine. Physiological and pathophysiological significance of tricuspid muscle may reside in its participation in valve closure during ventricular contraction and the fact that it is a site of abnormal impulse formation.

Acetylcholine↗

PubMed1980

An intracellular study of chemosensory fibers and endings.

1. The carotid body and its nerve, removed from anesthetized cats, were placed in physiological saline flowing under paraffin oil. The nerve, lifted into the oil, was used for either electrical stimulation or recording of the total afferent discharge. Intracellular recordings were obtained from individual nerve fibers and endings within the carotid body. The recording sites were identified by injecting Procion yellow through the intracellular electrodes; the tissues were then prepared for histology and observed with episcopic fluorescence or Nomarski optics. 2. Intracellularly recorded chemosensory fibers conducted at 1.1-30 m/s and usually displayed action potentials of regular amplitude. At times, however, some spikes become partially blocked while others maintained their original amplitude. "Natural" (hypoxia) or chemical (ACh or NaCN) stimulation induced different patterns of frequency changes of the large and small action potentials. This indicated nerve fiber branching at some distance from the recording site. 3. Intra- and extracellularly recorded spikes were blocked in 0 [Na+]0 by tetrodotoxin (TTX) or procaine. 4. During chemical stimulation, a slowly occurring depolarization (receptor or generator potential) was recorded intracellularly from the afferent fibers. It developed concomitantly with the increase in discharge. 5. Impalement of single nerve terminals (histologically identified) showed numerous "spontaneous" depolarizing potentials (SDPs) that had a mean amplitude of 5.6 mV, a mean duration of 46.1 ms, and nearly random distribution. They increased in frequency and summated during chemical stimulation. SDPs originated from either the site of recording or from neighboring areas. When the SDPs attained a certain amplitude, they seemed to give rise to action potentials. Also, relatively well developed or partially blocked spikes (apparently originating elsewhere) were recorded from single nerve terminals. 6. The receptor (generator) potential of chemosensory receptors appears to be an integrated response formed by multiple activity originating in different nerve endings.

Acetylcholine↗